FORTUNE — Underemployment — defined as doing a job for which one is overqualified, or involuntarily working part-time instead of full-time — gets less attention than outright unemployment, but there’s no denying it’s a problem: The Bureau of Labor Statistics reports that about 9.3 million Americans who want to find full-time jobs are doing part-time work as a stopgap, double the number who did so in (pre-recession) 2007.

Some people find themselves underemployed before their careers have even gotten off the ground: In 2009 and 2010, one survey found, 40% of new college grads took jobs that don’t require a college degree.

Yet it seems that underemployment needn’t be a permanent setback. Many thanks to everyone who responded to my recent query. Among those who emailed their stories, two main threads emerged: Using temporary work as a steppingstone to a permanent position, and treating a step down as a chance to learn a new career.

Bill Driscoll, a district president at accounting and finance staffing firm Robert Half International, is the first to admit that temping “can be a major morale killer.” But, he adds, “Every job is an opportunity, even if it isn’t your dream job. It’s a chance to showcase your skills, gain new ones, and grow your network. We do see lots of people turning contract assignments into ‘real’ jobs. It does happen.”

A case in point: Nicole White, who quit a full-time job in California where she managed a team of 20 employees doing fundraising for nonprofits, and moved to Florida when the military relocated her husband there. White could not  find a position like the one she left, so she signed on with a temp agency and took a $9-an-hour, no-benefits, 30-hours-a-week customer service assignment at a bank.

The work didn’t require her management skills: “I was answering phones for four or five hours a day and transferring money for people who couldn’t use a computer.” Still, she put her best effort into it. Several months later, her efforts paid off. Last March, White was hired by her county’s economic development office, “with salary and benefits at the level I was used to in California.”

Unbeknownst to White, a senior manager at the bank was also an influential board member at the county agency (and now chairs it) and was impressed by her performance as a customer service rep and called her in for an interview.

“Never underestimate the power of good work in any position you are offered,” says White. “You never know who is looking on.”

Some readers report they’ve deliberately taken a step down in status and pay in order to move their careers in a different direction. “I’ve done it more than once over the past 30 years,” writes Mike Frederick. Most recently, in 2007, when his department was eliminated, he turned down a couple of promotions to take a lower-paying staff job in his employer’s corporate university.

“No one could promise me I’d ever get back to my previous level of management in that department,” he recalls. Not only that, but the job called for tech skills that Frederick lacked. “I had a lot to learn and the odds against my success seemed daunting,” he recalls. Even so, his employer funded a series of courses he needed to take: “What clinched it was the chance to learn a new career at no expense to me.”

Fast-forward three years and, “after many long nights of studying on my own and hard work during the day applying what I learned”, Frederick is “at the point where I wanted to be,” he writes: In a management position in an IT training department.

What the experience taught him, he says, is that “taking a step down may be your best bet for ultimate success.” Frederick’s advice: “Find out if your company is willing to provide the training you need or will pay for college courses. Don’t be afraid to ask and, after you make the move, don’t look back. Focus on the possibilities ahead of you.”

As with any other challenge, getting past underemployment is sometimes a matter of sheer persistence. “I got bounced out of a great executive-assistant position at a brokerage firm when my boss got laid off in 2008,” writes Sheila Markson. “It took almost two years of pounding the pavement by day and waiting tables at night just to pay the rent, but I now have an even better job at an insurance company.

“This economy is discouraging,” she adds, “but the worst mistake anyone can make is to give up.”

Or, as Bill Driscoll puts it: “Never stop looking for the job you really want.” That’s wise counsel whether you’re currently underemployed or not.

Talkback: Have you ever bounced back from a spell of underemployment? What worked for you? Leave a comment below.